This invention relates to placement and removal of full-length or shortened ureteral stents, or stents in other hollow or tubular structures, which stents may be removed by means of a magnet.
Ureteral stents are used to provide drainage of urine from the kidneys to the bladder. The stent is a flexible, tubular structure that is constructed of relatively inert material. The stent is perforated to have a plurality of small drainage holes along its length. Some stents are shaped to define xe2x80x9chooksxe2x80x9d at either end. The hooks prevent migration of the tube from the kidney toward the bladder or from the bladder upwards.
Normally, indwelling stents must be periodically removed or replaced. Conventional stent removal procedures are complex and may be painful, sometimes requiring general anesthesia.
The presence of a stent within the lower ureter and within the bladder may cause considerable irritation to some patients. To alleviate this irritation, stents can be shortened. The stent is shortened at the distal (bladder) end. Thus, the distal end of the shortened stent resides in the ureter, remote from the bladder and the ureteral orifice. The ureteral orifice is the junction of the ureter and the bladder. A thin thread may be attached to the shortened stent to extend into the bladder and provide a means for later removing the stent. To remove the shortened stent, the thread must be endoscopically visualized, grasped, and withdrawn. Although this is a relatively simple procedure, it requires specialized instruments used by an urologist in a sterile setting. Here, too, general anesthesia is sometimes required.
Procedures for non-surgical removal of magnetically-attractible objects from a body cavity or tube have been used in the past. For example, U.S. Pat. No. 4,790,809 to Kuntz discloses a specially configured stent that carries a magnetically attractive tip. The tip is fastened to the hooked, distal end of the stent, which end resides in the bladder.
To remove the Kuntz stent, a catheter having a magnetized end is introduced into the bladder to attract and connect to the special tip of the stent. Apparently, the tip of the Kuntz stent may be caught by the magnet-tipped catheter in a manner that permits complete removal of the stent upon withdrawal of the catheter. Otherwise, Kuntz notes that the catheter and stent combination may be withdrawn just enough for the hooked end of the stent to be reached with a forceps or other grasping device, then completely removed. Apparently, Kuntz does not contemplate shortened-stent placement and removal.
The present system provides a stent assembly, system, and method for placement of ureteral stents, and for non-surgical removal of the stent assembly.
As one aspect of the invention, a conventional stent is modified to have connected to it a ferromagnetic member. The ferromagnetic member is biocompatible and is in the form of an elongated bead and is connected to the distal end of the stent by a tether. This permits the ferromagnetic member to be disposed in the bladder, suspended from the stent while the stent is positioned in the ureter. The bead is inserted at the time of insertion of the stent via a standard cystoscope that includes a guide wire and pusher.
The stent may be shortened to a length of choice prior to insertion, or left full-length. The shortened stent and tethered bead are inserted as a unit. The bead is shaped to temporarily penetrate the ureter as the bead is pushed with the shortened stent into the ureter to the desired position of the stent. The bead is provided with a mechanism that permits only the bead to be withdrawn from the ureter, pulled back into the bladder under visual control, once the shortened stent is properly positioned.
If a full-length stent is used, the bead does not, even temporarily, penetrate the ureter.
The stent assembly is readily removed by a non-surgical procedure that involves blind insertion of a magnet-tipped catheter into the bladder. The magnet engages the ferromagnetic bead, and the overall stent/tether/bead assembly is easily removed as the catheter is withdrawn.
As another aspect of this invention, the tether is flaccid, thereby permitting the suspended bead to move relative to the indwelling stent. This arrangement minimizes patient irritation that might otherwise occur if the tether were somewhat rigid or resilient.